System and Method for Utility Sampling for Trust Metrics in Pki

2. The method of claim 1 , wherein said probability p and confidence c associated with each edge K A →K B are calculated using utility sampling.

3. The method of claim 2 , wherein using utility sampling comprises A acquiring over a time interval r positive observations and s negative observations of a reliability of information provided by B, wherein said edge probability p = ( r + 1 r + s + 2 ) and said edge confidence c=r+s.

4. The method of claim 1 , wherein a total probability associated with an authentication path that terminates at said target key K T is a product of the probability of each edge in said authentication path, and a total confidence associated with said authentication path that terminates at said target key K T is a minimum value of the confidence values associated with each edge of said authentication path.

5. The method of claim 1 , wherein calculating said limit l on an amount of insurance for said one or more authentication paths ending with target public key K T comprises calculating a maximum K S -K T flow f in said directed graph, with a flow capacity on each edge being the c value of the edge.

6. The method of claim 5 , wherein calculating a premium for each amount m<l further comprises: sorting the authentication paths in increasing order of rate S i , wherein said authentication paths are labeled P 1 to P n in increasing order of rate s i wherein n is a number of authentication paths; and calculating said premium for said amount m<l from said sorted premium rates S i .

7. The method of claim 6 , wherein calculating said premium for said amount m<l comprises insuring a first f 1 dollars out of m according to P 1 using rate s 1 , and insuring subsequent amounts using each successive path P i using rate s i until all m dollars are allocated.

8. The method of claim 6 , wherein calculating said premium for said amount m<l comprises insuring a first f 1 dollars out of m at an average premium rate over all paths P i , and insuring subsequent amounts an average premium rate excluding a rate associated with the amount already insured, until all m dollars are allocated.

9. The method of claim 1 , further comprising: providing a list K T1 , . . . , K ti , . . . , K Tn of all public keys that B is attesting, wherein (p i , c i ) are the (p, c) values estimated by B about K Ti ; having A attest T i for each i via B after a time period using Δc i additional samples wherein Δr i of the samples show positive behavior by T i ; and updating the probability associated with each edge K A →K B from p K A → K B ← p K A → K B + ∑ i ⁢ Δ ⁢ ⁢ c i ⁡ ( 1 -  1 - Δ ⁢ ⁢ r i ⁢ p i Δ ⁢ ⁢ c i  ) c K A → K B + ∑ i ⁢ Δ ⁢ ⁢ c i , and the confidence associated with each edge K A →K B from c K A → K B ← c K A → K B + ∑ i ⁢ Δ ⁢ ⁢ c i .

11. The method of claim 10 , wherein a total probability associated with an authentication path that terminates at said target key K T is a product of the probability of each edge in said authentication path, and a total confidence associated with said authentication path that terminates at said target key K T is a minimum value of the confidence values associated with each edge of said authentication path.

13. The computer readable program storage device of claim 12 , wherein said probability p and confidence c associated with each edge K A →K B are calculated using utility sampling.

14. The computer readable program storage device of claim 13 , wherein using utility sampling comprises A acquiring over a time interval r positive observations and s negative observations of a reliability of information provided by B, wherein said edge probability p = ( r + 1 r + s + 2 ) and said edge confidence c=r+s.

15. The computer readable program storage device of claim 12 , wherein a total probability associated with an authentication path that terminates at said target key K T is a product of the probability of each edge in said authentication path, and a total confidence associated with said authentication path that terminates at said target key K T is a minimum value of the confidence values associated with each edge of said authentication path.

16. The computer readable program storage device of claim 12 , wherein calculating said limit l on an amount of insurance for said one or more authentication paths ending with target public key K T comprises calculating a maximum K S −K T flow f in said directed graph, with a flow capacity on each edge being the c value of the edge.

17. The computer readable program storage device of claim 16 , wherein calculating a premium for each amount m<l comprises: sorting the authentication paths in increasing order of rate s i , wherein said authentication paths are labeled P 1 to P n , in increasing order of rate s i , wherein n is a number of authentication paths; and calculating said premium for said amount m<l from said sorted premium rates s i .

18. The computer readable program storage device of claim 17 , wherein calculating said premium for said amount m<l comprises insuring a first f 1 dollars out of m according to P 1 using rate s 1 , and insuring subsequent amounts using each successive path P i , using rate s i until all m dollars are allocated.

19. The computer readable program storage device of claim 17 , wherein calculating said premium for said amount m<l comprises insuring a first f 1 dollars out of m at an average premium rate over all paths P i , and insuring subsequent amounts an average premium rate excluding a rate associated with the amount already insured, until all m dollars are allocated.

20. The computer readable program storage device of claim 12 , the method further comprising: providing a list K T1 , . . . , K ti , . . . , K Tn of all public keys that B is attesting, wherein (p i , c i ) are the (p, c) values estimated by B about K Ti ; having A attest T i for each i via B after a time period using Δc i additional samples wherein Δr i of the samples show positive behavior by T i ; and updating the probability associated with each edge K A →K B from p K A → K B ← p K A → K B + ∑ i ⁢ Δ ⁢ ⁢ c i ⁡ ( 1 -  1 - Δ ⁢ ⁢ r i ⁢ p i Δ ⁢ ⁢ c i  ) c K A → K B + ∑ i ⁢ Δ ⁢ ⁢ c i , and the confidence associated with each edge K A →K B from c K A → K B ← c K A → K B + ∑ i ⁢ Δ ⁢ ⁢ c i .

22. The computer readable program storage device of claim 21 , wherein a total probability associated with an authentication path that terminates at said target key K T is a product of the probability of each edge in said authentication path, and a total confidence associated with said authentication path that terminates at said target key K T is a minimum value of the confidence values associated with each edge of said authentication path.